China's President Xi Jinping (back L) and his South Korean counterpart Park Geun-hye (back R) attend a signing ceremony after a summit meeting at the Blue House in Seoul July 3, 2014. REUTERS/Ed Jones/Pool

(reuters_tickers)

By Jack Kim and Ju-min Park

SEOUL (Reuters) - The leaders of South Korea and China on Thursday restated their firm opposition to the nuclear ambitions of North Korea, Beijing's erstwhile ally, and to work towards concluding talks on a free trade deal by the end of the year.

Chinese President Xi Jinping's visit to Seoul, his fifth meeting with the South Korean leader since they both took office last year, seeks to strengthen commercial and diplomatic ties.

It is also aimed at reassuring Seoul and President Park Geun-hye that it would continue to pressure Pyongyang against its drive to acquire nuclear arms.

The events in Seoul will be watched closely in the North, which has test-fired short-range missiles and rockets from its east coast three times in the past week and threatened on Thursday to continue doing so.

Western countries, led by the United States, have pressed China to exert more pressure on North Korea to halt the nuclear and missile tests which have prompted the United Nations to impose sanctions.

Xi and Park, appearing briefly before reporters after their talks, said they were firmly opposed to nuclear weapons on the Korean peninsula.

Xi made no mention of North Korea by name, a standard practice in Chinese diplomacy. Neither leader took questions.

"The two sides reaffirmed the position that they firmly oppose the development of nuclear weapons on the Korean peninsula," a joint statement said.

Both sides expressed support for the stalled six-party talks aimed at ending the North's nuclear progammes in return for economic and diplomatic rewards. Hosted by China, they also involve the two Koreas, Japan, Russia and the United States.

LITTLE PROGRESS IN TALKS

These sporadic talks have made little progress. They collapsed in 2008 and North Korea declared them dead. It has since reversed position and expressed willingness to return, although Seoul and Washington are reluctant to go back to the table.

The North describes the weapons it is developing its treasured sword. It periodically threatens to attack the South and its U.S. ally, interspersed with periods of apparent concessions. China is believed to be growing increasingly impatient with North Korea's missile and nuclear programmes, and last year backed the latest round of U.N. sanctions against Pyongyang.

But it does not want to see the collapse of the isolated state, which could unleash turmoil on its borders.

Xi has yet to meet North Korean leader Kim Jong Un, the third generation of his family to rule the country.

China and South Korea launched free trade talks in 2012 but face hurdles in agreeing on the removal of tariffs on industrial goods and agricultrual products.

The two countries' trade totalled $230 billion (134 billion pounds) last year and Xi was accompanied on his two-day visit by a delegation of Chinese business heavyweights.

"The two sides appreciated the progress in negotiations to reach a comprehensive free trade agreement at a high level and agreed to strengthen efforts to conclude the negotiations by the end of the year," the joint statement said.

The two leaders also agreed on a series of steps aimed at spurring offshore use of the yuan and investment in Chinese capital markets.